Z-Order overview

Each Primitive has a Z Position, which is determined automatically by the Canvas2D Engine and can be overridden if needed.

The actual Z Position can be retrieve by calling the getActualZOffset method which return a number between 0 and 1.

• 1 means below everything.
• 0 means on the top of everything.

Default behavior

A primitive will be drawn on the top of its parent, its previous sibling and their parents.

Which means if you have the following hierarchy of primitives:

• Canvas
  • PrimA
    • PrimA-Child1
    • PrimA-Child2
    • PrimA-Child3
  • PrimB
    • PrimB-Child1
    • PrimB-Child2
    • PrimB-Child3
  • PrimC
    • PrimC-Child1
      • PrimC-Child1-SubChild1
    • PrimA-Child2

It means:

• PrimB will be over the Canvas, PrimA and PrimA's children (PrimA-Child1/2/3).
• PrimB-Child1 will be over PrimB (and also over what PrimB is over).
• PrimB-Child2 will be over PrimB-Child1 (and also over what PrimB-Child1 is over).
• And so on, you get the idea.

Changing the order between siblings

For example if you need to move PrimB-Child1 over the top of PrimB-Child2 & PrimB-Child3 all you have to do is call the Prim2DBase.moveChild method like this:

PrimB.moveChild(PrimB-Child1, PrimB-Child3);

This call will reorder the list of children to put Child1 after Child3, ensuring a rendering on the top of both Child 2 and 3.

Overriding the Z-Order

The zOrder property can be set to override the default value computed using the place of the Primitive in the hierarchy. When set the getActualZOffset method will return its value.